I have now listened more. Dynamic range is expanded much. The bridge sounds also somewhat more open so i needed some time to find the right cabling and adjustment of the subwoofer. It has 6db more gain to begin with so initial impressions may have being spoiled somewhat by too low gain in the subwoofer chain. The slightly sweat character of the unbridged version is gone. It sounds basically very neutral with good resolution. That can be because i reduced the bias somewhat or it is an effect the bridge has on the distortion spectrum. Theoretical the bridge should suppress second harmonic.
For now i am satisfied. More to come.

I have worked with Ward Maas on finishing the circuitry of the SBP. The bias scheme is now automatic. Ward also choose the NE5534 because it can be run on plus-minus 20V for more power without bridging. An LME49870 can be used for even more power because it can stand plus-minus 22V.
Holger had a nice idea how a bridging adapter can be avoided : Use a balanced line stage.
I found a circuit that can be used or modified.

Circuit 112 ( left ) works without problems. You can do things in the PSU. I am using a Nelson Pass cap multiplier but a conventional PSU ( transformer, bridge, elcaps ) will work too.
Only the output transistors are on cooling profiles.

T3, T4, T7, T8 form a bipolar current source. The configuration as a symmetrical Widlar mirror makes sure that the same current appears on both output nodes.
This amp has no VAS as such. The opamp provides most of the voltage gain.
The current mirror gives a high impedance for the opamp helping linearity by not much loading the opamp. This also maximizes open loop gain and gives some PSU rejection.
There is some voltage gain in the OPS but it is localized. This is a Szikley ( CFP 100% current feedback ) where the current comes
out of the collectors of the ouput transistors. This is a bit like Theshold Stasis but with the Szikley wrapped in an overall voltage feedback loop.
T9, 10, 11, 12 form a string of Ube transdiodes making the output stage conduct. The Szikley OPS does not need much idle current so this is close to class B. You can increase the idle by adding Ube diodes in the string. You can measure the idle in R15, 16.
R13, R14 provide overall voltage feedback, C9,10 block DC so DC gain of this amp is only x 1. That makes a servo obsolete.
You can use a foil cap instead of C1,3.
I can not remember what the jumper is for. It breaks the base current on the negative side so this output transistor does not conduct any more. It may have to do with testing.

One is audio ground, the other cabinet ground when it is from metal.
R11 sets the input impedance. You can make that higher ( up to say 47kOhm ) if you wish but 10kOhm is less prone to noise injection.
R12 forms a low pass with C2 to roll go HF.
Yes, you can use 4562. We close NE5534 because it can stand up to plus-minus 22V so the amp has enough power. There is an opamp from National in the same series then 4562 that also can stand more voltage.
You can use a Fet opamp like the OPA1641 but watch the maximum PSU voltage allowed.